Anime about demons?????

Inuyasha

Ao no Exorcist

Not quite clear... but Ghost Hunt is a good Anime if te like Supernatural shows.

XXXHolic and Black Butler have demons and spirits in these series

Naruto and Naruto Shippuden (Tailed Beast)
Amatsuki (Demons, gods)
Hakuouki (Historical, Fantasy, Demons)
Yu Yu Hakusho (spirit world, ghost, demons)
Natsume Yuujinchou (Yokai- ghost, demons, evil and good)
Psychic Detective Yakumo (ghost)


[pictured] Saiyuki ("Journey to the West" with a twist, demons... lots)- This is an older Anime (2000), The story of four anti-heroes: the monk Genjyo Sanzo, the monkey king Son Goku, the half-demon Sha Gojyo, and the man who turned into a demon Cho Hakkai. They have to travel westward to India to stop the magic that is making all the demons go mad.
Been a while since i've seen it but it was fun to watch, pure adventure and fighting off demons.

07 Ghost
Ao No Exorcist
Makai Ouji Devils and Realist
Kyou Kara Mahou
Inuyasha
Beelzebub
Otome Youkai Zakuro
Kamisama Hajimemashita
Inu X Boku SS
Hakuouki
D. Gray Man
Natsume Yuujinchou

Those are all really good and related in some way to demons, spirits, o youkai :)

Hellsing
Black Butler

Kuroshitsuji